Above Ground Pool Filter Problem

[BigDave]

That is a pretty small filter and a pretty big pump. Can you provide the model number of the pump? 1.5HP could really be 1HP or less - There's all sorts of shenanigans surrounding pump ratings especially AG pumps.

[CarlD]

Big Dave is right. Even the MOST up-rated 1.5hp pump is probably too big for a 100# sand filter. At a guess, I would say that your laterals in the filter have been damaged by too much pressure. There are a few solutions if that's the case:
1) Replace the filter with a bigger one, like the 200# or 250# filter--it's always better to have a filter that exceeds the pump's capacity, but I'm assuming an up-rated 1.5, not full-rated, in which case even a 250# MIGHT be too small.
2) Replace the laterals and get a smaller pump.
3) Replace the laterals and get a low-flow impeller for the pump.

BUT--try the DE test first--that's a $10-$15 investment vs the cost of a new filter or pump.

Carl